Reduction of acrylamide formation

ABSTRACT

The invention relates to the use of acid treatment of uncooked French fries prior to cooking by roasting, frying, grilling or baking whereby to reduce the acrylamide content of the cooked product.

The present invention relates to improvements in and relating to Frenchfries.

In a publication by the Swedish National Food Administration (seewww.slv.se/engdefault.asp) it was reported that many cooked foods, inparticular fried, grilled or baked foods, had surprisingly been found tocontain high levels of the toxic contaminant acrylamide. No suggestionwas made as to how the acrylamide context of such foods could bereduced.

A further report of acrylamide production in food cooking occurred inTareke et al., J. Agric. Food Chem 50: 4998-5006 (2002).

We have now surprisingly found that the acrylamide content of Frenchfries can be reduced by treatment of the French fries prior to cookingwith lactic acid generating microorganisms and/or with acid.

Thus viewed from one aspect the invention provides the use of a lacticacid producing microorganism for the treatment of uncooked French friesor flour for use in the preparation of uncooked French fries to reduceacrylamide production in subsequent cooking thereof.

Lactic acid producing microorganisms are well known and examples includelactic acid bacteria such as Bifidobacterium sp., Brevibacterium sp.,Lactobacillus sp., Lactococcus sp., Leuconostoc sp., Micrococcus sp.,Oenococcus sp., Pediococcus sp., and Streptococcus sp. Lactobacilli areespecially preferred for use according to the invention, in particularLactobacillus plantarum strains NCDO 1752 and NCDO 1193 (available fromthe National Collection of Food Bacteria) and Lactobacillus NCIMB 40450.Other strains of lactobacillus which generate lactic acid and are safefor use in foodstuff treatment have been described widely in thescientific literature.

The treatment with a lactic acid producing microorganism according tothe invention preferably involves incubation in an aqueous medium for upto 7 days, e.g. 30 minutes to 24 hours, especially 1 to 6 hours.Incubation is preferably at 4 to 45° C., e.g. 25 to 35° C., i.e. as isconventional for such microorganisms.

Typically such treatment may involve homofermentative lactic acidbacteria incubation in an aqueous medium.

Viewed from a further aspect the invention provides the use of aphysiologically acceptable acid for the treatment of uncooked Frenchfries or flour for use in the preparation of uncooked French fries toreduce acrylamide production in subsequent cooking thereof.

The physiologically tolerable acid used according to the invention maybe any acid acceptable for use in foodstuffs, e.g. organic acids, suchas citric, malic, acetic, maleic, tartaric, succinic and lactic acids orinorganic acids such as hydrochloric, sulphuric and phosphoric acids andsulphur dioxide. The use of citric and hydrochloric acids is especiallypreferred, as is the use of lactic acid and/or of phosphoric acid. Theuse of hydrochloric acid is especially preferred. The acid is preferablyused in a quantity and strength sufficient to reduce the surface pH ofthe uncooked French fries treated to 1 to 5.5, preferably 3 to 5,especially about 4. Following acid treatment, the uncooked French friesare preferably stored for up to 7 days (e.g. 30 minutes to 24 hours,especially 1 to 6 hours before cooking or freezing.

In this process, the acid is preferably used in the form of a buffersolution.

Following treatment with the acid and/or the lactic acid producingmicroorganism, the uncoooked French fries may be cooked using cookingtechniques that expose the product to temperatures above 150° C., e.g.by baking, grilling, roasting or frying.

Before such high temperature cooking, it is desirable to rinse thetreated uncooked product with water.

The cooking may be a single stage operation. However it may instead beone stage of a multi stage (e.g. two stage) cooking procedure. Thus thetechnique of the invention is especially applicable to French frieswhich are treated according to the invention, partially cooked,transported and/or stored, then cooked again.

Where appropriate, the products produced according to the invention maybe further processed, e.g. by drying, freezing, sealing into moistureproof containers etc. Such processing steps, which are oftenconventional for French fries, form further optional steps in theprocesses of the invention.

The invention is especially applicable for the production of so-calledoven-ready french-fried potatoes which are provided to the consumer inpart-cooked form for baking prior to serving, as well as to theproduction of chopped ready-to-fry potatoes (e.g. of the type producedfor deep frying in restaurants).

Thus viewed from a further aspect the invention provides a process forthe preparation of ready to cook (e.g. oven-ready or ready to fry)french fried potatoes which process comprises chopping potatoes,fermenting the chopped potatoes with a lactic acid producingmicroorganism, frying the fermented chopped potatoes, and optionallyloading the fried fermented chopped potatoes in a container, andoptionally sealing the container.

Viewed from a still further aspect the invention provides a process forthe preparation of ready to cook (e.g. oven-ready or ready to fry)french fried potatoes which process comprises chopping potatoes,treating the chopped potatoes with a physiologically acceptable acid,frying the acid treated potatoes, and optionally loading the friedpotatoes into a container, and optionally sealing the container.

The chopping stage in this process is preferably such as to producebatons having a cross-sectional area of 10 to 100 mm², especiallypreferably 25 to 80 mm².

The container used in these processes will typically be a plastic bag,paper carton or bag or other container conventionally used for storageand transport of ready to cook french fries.

Viewed from a still further aspect the invention thus also provides acontainer containing ready to cook (e.g. oven-ready or ready to fry)french fried potatoes produced by frying chopped potatoes pre treatedwith a lactic acid producing microorganism and/or with a physiologicallyacceptable acid.

French-fries are preferably made from sliced potato; however they mayalso be made from extruded or moulded carbohydrate-containing pastesproduced using powdered or granulated potato and/or cereal (e.g. rice).

Thus in alternative aspects of the invention the uncooked French friesmay be produced from potato and/or cereal flour fermented with a lacticacid producing microorganism or treated with an acid as described hereinbefore being moulded or extruded in paste form into French-fry shapesand then cooked. If desired, the fermentation or acid treatment may beeffected on French fry shapes moulded or extruded using a potato and/orcereal flour based paste.

The potatoes treated according to the invention are preferably of avariety selected from Maris Piper, Beate or Russet, especially MarisPiper. Saturna, King Edward, Russet Burbank, Bintje, Shepady and Shastamay also be used. Especially preferably the potatoes are selected fromvarieties having a reducing sugar content of less than 1.5% wt,particularly less than 1.0% wt.

Besides the fermentation and/or acid treatment according to theinvention, the French fries of the invention may be prepared byconventional methods, optionally involving rinsing and/or drying afterthe treatment. Thus such French fries may optionally containfurther,components, such as conventional foodstuff components oradditives, e.g. salt, sugars, flavours, stabilizers, buffers, etc.

The invention will now be illustrated further with reference to thefollowing non-limiting Example.

Example 1 French Fries

Ingredients

Potatoes of the variety Beate were obtained from Department ofHorticulture and Crop Sciences, Agricultural University of Norway, As.The potatoes were stored at 8° C. from harvest until three weeks priorto processing when storage temperature was reduced to 4° C.

Palm oil was obtained from Denofa AS, Frederikstad, Norway. The oil hadmaximum 0.05% free fatty acids, an iodine number of 60, a peroxide valueof 0.5 mekv/kg and an anisidin number of 5.0. Fatty acid compositionwas: 12% linoleic acid, 42% oleic acid and 45% saturated fatty acids.

The Lactobacillus strain NCIMB 40450 was used. Bacteria cells were grownand harvested in the logarithmic growth phase by centrifugation andresuspended in 1% salt brine. The soaking solution used was: Brine forfermentation: 1% NaCl with the addition of bacteria until 1×10⁶ cells/ml

Pre-Treatment of Potatoes

Potatoes (var. Beate) were peeled and cut with a knife into 6×6-mmsticks. The sticks (200g) were immediately added to 400 mL of brine.Fermentation was allowed to proceed in an incubator at 30° C. for 5 hrs.Control samples were rinsed in water and deep-fried without delay.

Deep frying

The potatoes were dried with paper towels and deep-fried as 150-gportions in palm oil at 170° C. in a Nuovo Elframo, Model EB (Bergamo,Italy) fryer for 8 min.

Analyses

Dry matter was determined in a vacuum oven at 70° C. over-night. pH ofbrines was determined using a pH-meter. Soluble solids of potatoes weredetermined as ° Brix using a Metler Toledo RE40 refractometer. Sampleswere homogenised and a few drops of the homogenates were applied on therefractometer. ° Brix is given as g sucrose/100 g sample.

Accredited analyses of acrylamide were carried out at SteinsLaboratorium, Denmark.

Results

The °Brix-value of the potatoes (var. Beate) was 6.8.

Results from the analyses of deep-fried products are shown in Table 1below. TABLE 1 Dry matter pH in brine g/100 g μg/kg Acrylamide afterpre- fried dry μg/kg % reduction Pre-treatment treatment product matterproduct (product) control  6.7* 86.0 744 640 0 fermented 4.3 85.3 469400 38*tap water

The samples within each of the product groups were deep-fried for thesame period of time, rather than being deep-fried until a certainproduct colour. Any difference in acrylamide levels thus reflects theability of the treatment to prevent the formation of acrylamide,regardless of the colour that might be formed during deepfat-frying.

1-4. (canceled)
 5. A process for the preparation of ready to cook frenchfried potatoes which process comprises chopping potatoes, fermenting thechopped potatoes with a lactic acid producing microorganism, frying thefermented chopped potatoes, and optionally loading the fried fermentedchopped potatoes into a container.
 6. A process for the preparation ofready to cook french fried potatoes which process comprises choppingpotatoes, treating the chopped potatoes with a physiologicallyacceptable acid, frying the acid treated potatoes, and optionallyloading the fried potatoes into a container.
 7. A container preferably asealed container, containing oven-ready french fried potatoes producedby frying chopped potatoes pre treated with a lactic acid producingmicroorganism and/or a physiologically acceptable acid.
 8. French friesproduced by a process as claimed in claim
 5. 9. French fries produced bya process as claimed in claim 6.